Very interesting . I love the proto BA set used to be an instructor on them Mk4 & Mk5, plus the Salvus 1/2 hour set. There used to be a rhyme for the start up procedure :- " While the dresser buckles you, pull out plug and mouth piece do. main valve lock it take a reading, nose clips, bypass do your breathing, protect your sight , get your light . Your alright. remember that from 50 years ago.Happy days

Replied on: 5:33pm 09-16-2017

Stephen, thanks for the ryme, very valueble, and thanks for visiting my website!

Saw a feature "on the waterways" I think with Jason Robards, that included and episode on the Gunilda. Spent several days thinking a ways to refloat the ship. I check on it every few years or so to catch up on the story. Thanks for your efforts.

The Breathing Apparatus was developed around 1926 as a refinement of the Gibbs rebreather , which was in use in Europe.

It was developed by George McCaa, a mining engineer by profession, who was my Grandfather's brother. It was manufactured and sold by the Mine Safety Appliances Corpoation in Pittsburgh Pa. Primarily for the mining industry. The unit was originally equipped with a mouth bit for breathing , similar to what is used on SCUBA gear. Later a full facepiece was provided, approved as "auxiliary equipment"

The original version was rated for two hours of use, and was worn on the back. The sloping cover was designed so the rescuer could carry anotyher person "piggy back" style. Later a one hour version was made, worn on the front. The time limitation was set by the ability of the "scrubber" or "regenerator" to remove Carbon Dioxide from the exhaled breath. It "breaks" quickly and after two hours, physiological problems were likely to occur. The scrubber was a chemical mixture which was packaged loose and separate from the unit in cans, so the unit had to be charged before use. Although used in mine rescue up until the 60's or 70's, the unit never became widely used by the Fire Service, most probably because of the time and trouble it took to charge it up, and also because the procedures for useage were quite meticulous to keep the unit from becoming Nitrogen or Carbon Dioxide bound.

Hi there,
I am Ted Eldred's Granddaughter and Tony Eldred's daughter. I am researching my Grandfathers invention at the moment, this website was very helpful and it was a great tribute. Thank you for supplying the knowledge that I'm sure will fascinate people for years.

Nice photos of the Mk 6 SCR used by the US Navy during the 1960's, and 70's.

Though the 32% O2 mixture was used to a depth of 55 metres (6,5 bar), you must kep in mind that Mass Flow SCRs have an important difference between the FO2 on the cylinder and the actual inspired FO2 moving around the loop. For many mass flow semi closed rebreathers, depending upon the metering valve and the diver's VO2, this reduction is about 10%. So even though 32% nitrox is used, the gas actually inspired by the diver will be closer to 22%. This FO2 at 55 metres gives us a pO2 of 1,43 bar.

Also, of the copied manual pages, only the first one is about the Mk 6 SCR, the other ones are about the Emerson O2 CCR, which from the front looks similar to the Mk 6 SCR. The Mk 6 has two cylinders with a canister nested between them, and no "box" or container, just a backplate. The Emerson CCR O2 has only one cylinder and a canister lodged one beside the other in a cover or box.

Another difference is that the CCR is controlled by the diver by means of a metering system attached to the right-hand side of the unit's vest. The Mk 6 SCR doesn't have a metering device that can be accessed by the diver, instead it has a special pressure gauge that tells that allows the diver to see wether the injector if operating

I'D LOVE TO HAVE A COPY OF THE TECHNICAL MANUALS FOR THERE TWO REBREATHERS, and I'd much appreciate your letting know how I may get a copy of each of the two books'

I have been trying to find pictures or videos of the diving equipment I used in the Royal Navy during the 1970s and came across your site. I notice you have pictures of SABA, both as a closed circuit AIR (not oxygen as stated) system and as a re-breather. I'd like to point out that the cylinders are up side down. The reason they were the other way up was to enable the wearer to reach the equalising valve on the right hand tank. As the only pressure gauge was located on the frame this couldn't be used to determine how much gas remained. The drill was to have the left tank open and the right was the reserve. The left tank would be breathed down "dry" , the diver would stop breathing and the equalising valve opened, once pressures were equalised the valve would be closed and breathing would continue until "dry" again, equalising drill would be done as before. At this time the diver would surface having 25% air remaining. Endurance on the set was around 50 minutes, for the average dive operating at normal working depth, 15 = 30 feet at maximum capacity was 120 bar. The only video I've found is on youtube search "DEEP DIVING TRIALS (1965)" which shows, albeit briefly the sets configuration. It was a fabulous piece of kit to dive in with a weight pouch at the front and a box at the back, which put the weight exactly where it was needed, in the centre of the torso. Congratulations on your excellent site. I hope you find this useful. Les